Fuel injection system



Sept. 15, 1959 A. c. KORTE FUEL INJECTION SYSTEM Filed April 29, 1957yl-lff fr INVENTOR. ALFRED C. KORTE ATTORNEY United States Patent FUELINJECTION SYSTEM Alfred C. Korte, St. Louis, Mo., assignor to ACFIndustries, Incorporated, New York, N.Y., a corporation of New JerseyApplication April 29, 1957, Serial No. 655,631

Claims. (21. 123-479 This invention is an engine fuel charging deviceoperating as a continuous flow system adapted for intake port injection,in which system the fuel is pressurized, measured under pressure inaccordance with engine requirements, and distributed under pressure topoints adjacent the intake valves of the several cylinders or combustionchambers of the engine. This application shows an improvement applicableto the basic system shown in the prior patent to James, Fred Armstrong,No. 2,785,669, dated March 19, 1957, entitled Injection Carburetion.

A more complete understanding of the invention herein disclosed will behadby reference to prior applications of James Fred Armstrong, SerialNo. 632,798, filed January 7, 1957, for Fuel Injection System, andSerial No. 646,062, filed March 14, 1957, for Fuel Injection System, nowPatent No. 2,846,994. I

The improvement disclosed herein may be applied to any of these priorinventions, as well as others which function on similar principles.

This application is specifically directed to features including a fueldelivery cut-off operated by the ignition switch, an engine loadoperated means for shutting oil. the fuel during deceleration of theengine from high speeds, and a control for changing the fuel deliveryfrom the nozzles during engine cranking, which normally increases theflow to prime the engine, or, on full throttle opening, cuts off thefuel flow completely.

These features are all disclosed in the last-mentioned application byJames Fred Armstrong, and the improveand has a metering screw 78 foradjusting the amount of ment here includes electrical circuits forperforming the DESCRIPTION Air flow metering The air metering ormeasuring part of this system, indicated as B in Fig. 1, may be placedanywhere near the engine and connected with the inlet of the engineintake manifold, which has several branches (not shown) leading to theseparate intake ports of the engine. This air measuring or meteringpart, termed the air horn, has a tubular body constructed for connectionat its lower or outlet end to the intake manifold of the engine. Theoutlet of the air horn is controlled by a suitable throttle 50 mountedon a throttle shaft 51, and controlled by athrottle arm 52 actuated by alinkage R from the throttle pedal T.

Above the throttle is a balanced air valve 37 mounted on a suitableshaft 36 journaled in the walls of the air hem B. On the lower leadingedge of the air valve 37 is Patentd Se t. 15, 1959v 55-.- The valve 37is moved in the opening. direction by j a Servo-motor which has adiaphragm 40 operating against a calibrated spring 43 and a connection39 with the air valve 37. The servo-motor is powered by the pressuredrop across the air valve 37 as sensed -by two- Pitot tubes 44 and 45upstream and downstream of the" A slotted baffle 49 extends. between theair valve shaft 36 and the throttle shaft 51.

air valve 37, respectively.

in a manner to eliminate aerodynamic interference of the air bypassingthe air valve 37 in the idle range of displacements of this valve so asto adjust the mixture ratio at idle.

The air valve 37 is displaced by the power operated servo-motor so thatit takes up an angular position indicating the rate of air flow past thethrottle 50 to the engine. Shaft 36, upon which it is mounted, is inturn connected to the fuel metering part A by means of a magnetic clutch35 to control the displacement of a plu rality of tapered fuel meteringrods which are calibrated displacements of the air;

to flow fuel at a rate to give the full throttle power mixturethroughout the range of angular displacement of the air measuring valve37.

To get a part throttle economy mixture, the response of air valve 37 toair flow is modified to produce a de- Part throttle mixture Air valveresponse is modified for the above purpose by an air bleed connection205 in the air horn B which connects the plurality of ports 202 and 203above the air valve 37 to the suction side 42 of the servo-motor. Inthis connection is a diaphragm operated valve 212 which is'held openagainst the closing force of the spring 211 by suction connection 209extending posterior of the throttle valve 50. When the throttle is openfar enough 7 so that manifold depression is less than six inches Hg,-forexample, valve 212 is closed by the spring 211 against: the force ofsuction acting on the diaphragm 208, thus: cutting off the air bleed 205from communication with. the suction side 42 of the servo-motor. Theresponse of the air valve 37 is thus changed to increase its opening andthe displacement of the fuel metering rods to in-- crease the fueldelivery rate to a full rich mixture.

If, on the other hand, engine speed increases in thepart'throttle rangeof engine operation, angular air valve displacement is decreased for thesame rate of air flo'w, giving a lesser displacement to the meteringrods 33 so as.

to lean out the mixture for part throttle operation. '.As

engine speedincreases, however, angular airvalve displacements will alsoincrease as a result of increasing air flow, so that the edge of the airvalve 37 and deflector 37a m swings over the ports 202, and 203. Thisplaces the ports 202 and 203 in a zone of decreasing air pressure due tohigh velocity flow to reduce the effectiveness "of the air,

bleed on the action-"ofthe servo-motor. spouse is accordingly modifiedto increase air valve open Air'valve 're-' consequently, the rate offuel flow to the engine,

giving a richer mixture at higher engine speeds to eliminate thepossibility of part throttle detonation.

Mixture control for acceleration If the particular engine. requires aricher mixture on suddenthrottle opening, some kind ofa connection m ay.bed esirable, between the throttle, and the, fuel metering; rods to,increase. thefuel flow temporarily, In this device, it is moreconvenient to use an equivalent structure which;

operatesthe-air valve in an openingvdirectionupon openingoflthethrottle. Forexarnple, the air horn B has a pump with a.diaphragm127 spring-powered by a suitable ooil spring 128,-. and heldin: operative position with the spring; ;128 compressed bya connection.130 ,to the;.suc-. tion sideof the air horn below. or downstream of'thethrottle valye 50. The pressure side of the pump 125 is connected-by apassage 129 with'the pressure side 41 of the servo-motor. A leaf type ofcheck valve 200 controls the eseape of pressure from the Pitot= tube 44.

:Duringoperation of the engine at-idle. speeds, suction compressesthespring 128, but on throttle opening-this suction force largelydisappears, allowing the spring 128 to; expand, pumping air into thechamber 41 of. the servomotor to. displace the valve 37 in an-openingdirection, thus .withdrawing the metering rods33 to increasethe fuelmixture ratio, temporarily.

Starting mixture enrichment At low engine temperatures, fuel flow shouldbe increased for starting and engine warm-up. This result isaccomplished in the instant device by modification ofthe response of theair valve 37 instead of by direct connection with the fuel metering rods33 which is, of course, possible. hornB' mounts a thermostatic spring102 concentric with respect to one end of the air valve shaft 36. Oneend As illustratedvschematically herein, the air-- of the spring 102 isheld fast in a slot in a pivoted lever 101,.which in turn is angularlymovable by a suction operated piston 105 in a cylinder 106 against theforce of'a calibrated spring 107. Suction is communicated to thecylinder 106 through a line 108 communicating with the manifolddownstream of the throttle 50. The free end of the-thermostat 102,indicated as 103, abuts a lever100- fast on one end of the shaft 36,and, as the engine cools,

the thermostat 102 winds up, exerting a'force in a clockwise directionon the lever 100 to urge the valve 37 toward an open position. The forceof the thermostat depends upon the temperature, but at temperaturesbelow those encountered in normal operation of the engine this forceeither actually opens theair valve 37 or decreases theforce necessary toopen the valve, so that the servomotor produces a greater degree ofvalve opening andmetering rod movement for increasing the fuel flow tothe engine during cranking. As soon as the engine starts, suctionrotates the arm 101 to decrease this opening force exerted by thethermostat spring 102 on the arm ing .;the,throttle 50 at lowenginetemperaturesis shown ina copending application of James Fred Armstrong,

Serial No. 622,917, filed. November 19, 1956,;and.entitled; Fuellnjection System. Figs. 25 and 26 iof thisiappli cationillustrate thefastidlecontrol mechanism. The i structu e eanbe r sed e er al ug it isnetshe m i.

n orms- 0 Part. ofi hisu nr nt on-q Fuel metering system This part ofthe injection system may be conveniently described as having a fuelcharging circuit and a datum pressure circuit. Both circuits aresupplied with fuel under pressure from a pump P connected with a fueltank by the line 19. The output side of the pump P connects by way of acheck valve to a combined filter and pressure regulator 22 of the typeshown and described in the prior applications of James Fred Armstrongabove mentioned. The discharge from the pressure regulator 22 connectswith a fuel chamber A by way of a line 20a.

The engine charging circuit includes the pressure chamber A and aplurality of discharge lines 24 connecting the chamber with individualnozzles 25 which discharge adjacent the intake valves of the engine inthe branches of the manifold. The inlet of each fuel line 24 is suppliedwith fuel at the same pressure from the fuel chamber A through separatefuel metering jets or orifices 23, one for each of the fuel lines 24.Each meteringjet or orifice is variable in area by an individual,tapered metering rod '33, all supported on a. common carrier 34' formoving all of the rods in or out of the jets in unison.

Angular movements of the air valve 37 are mechanicah 'ly transmittedfrom the shaft 36 outside the chamber A to move the commoncarrier 34inside the chamber A bymeans of a, magnetic clutch having elements 35dis-. posedinside and outsideof the fuel chamber A. Movement of the rodsin unison varies the area of all of the fuel metering orifices 23simultaneously and equally.

Each of the fuel nozzles 25 is, in effect, a pressure regulatingtype ofvalve with an operating diaphragm 28, ex-

posed to the action of the pressure downstream of each. metering jet 23in the separate lines 24. Fuel pressure in each line 24 acts on thediaphragm of the valve in a valve opening direction.

The datum pressure circuit The opposite side of each of the diaphragms28 of each nozzle 25is connected toa by-pass fuel passage 56, 58 havingthe branches 58a, b, c, and a connecting with the individual fuelnozzles 25. The datum circuit is maintained under a pressure which bearsa constant relation to the chamber pressure (about a half toone-anda-half pounds gauge lower during operation). Since all of thenozzles are connected with the by-pass 58, the pressure on thediaphragms 28 resisting valve opening is equal in all of the nozzlevalves. When the pump and engine are in operation, each nozzle valvewill open until the pressures on opposite sides of eachdiaphragmbalance, or, stated another way, each nozzle valve 25 maintainsthe pressure downstream of each metering jet 23 equal to datum pressure.The pressure downstream of each metering jet is thereby maintained equalin allthe lines 24 by interconnection of all the'nozzle valves 25 to thedatum system. Each jet is likewise exposedto thesame pressure in thecommon supply chamber A,

so that equal division of the how through the branchesis obtained withjets of equal area operating at equalpressure drop.

In the datum pressure system is a pressure regulator C which controlsthe pressure upstream of the small metering orifice 61 at the by-passoutlet from the line 58. Between the orifice 61 andthe pump inlet is asecond pressure regulator 60.

Regulator C is supplied with fuel through a connection to the-fuelchamber A by line 56, and is set to maintain a constant relativepressure in the line 58 (about onehalfto one-and-a-half pounds gauge)below the pressure of fuelin the chamber A, Whatever that pressure maybe.

The regulator 60 is set to maintain a certain minimurmv pressure in thedatum line or by-pass, about twenty to twenty-two pounds. Together,these two regulators maintaina small, continuous flow throughtheby-passorv datum circuit and out orifice 61 to the pump. This.

am nes flaw insures circulation in the entire fuel metering system.

When fuel flow increases through the jets 23 in lines 24, the nozzlevalves must open. In order to avoid lag in fuel delivery as the meteringrods 33 are withdrawn from the jets 23, some provision must be made toac commodate the fuel displaced into the datum system circuit bymovement of the diaphragms 28 of each nozzle 25. This movement will beaccompanied with a slight pressure increase in the datum circuit 58,causing diaphragm 71 of pressure regulator C torespond, closing inletvalve 75 and opening outlet vavle 76, allowing the fuel to escapethrough a line 79 downstream of the metering restriction 61.

The preferred details of construction for the pressure regulators C and60 have been described in the prior applications of James Fred Armstrongabove mentioned. A further description here would be repetitious andserve no useful purpose, since the construction is not a feature of thisinvention.

Engine priming circuit In this system, the mixture ratio furnished maynot only be affected by modifying the response of the air valve, asabove described, but also by varying the pressure drop across themetering restrictions 23, and since this pressure drop or pressuredifferential is controlled directly by datum pressure, the mixture ratiocan be varied one Way or the other, rich to lean, by changes in thedatum pressure regulation. Because of this inherent characteristic ofthe system, it is possible to add to it the many desirable auxiliaryfeatures necessary to adapt the system to the needs of the engine.

, For example, the particular engine might require a rich mixture duringcranking in order to facilitate engine starting. This function can bebuilt into the present system by a control which acts upon datumpressure. The following detailed description is explanatory.

The usual starter and ignition circuit for the engine includes thebattery 194 connected at one terminal to ground, and at the otherterminal to the ignition key switch 197, which switch, when closed,energizes a circuit to the starter switch S, which is connected, inturn, by a lead 198 with the starter motor 195. Connected with the lead198 is a second lead 189 extending to the Winding on solenoid 173 in thepressure regulator 60 and to ground through the lead 188.

Operation of priming circuit To crank the engine, both the ignitionswitch 197 and the starter switch S are closed, so as to complete thecircuit to the engine starter motor 195. This circuit, in turn,energizes the circuit through the solenoid 173 by way of the leads 189and 188, energizing the solenoid 173 and producing a magnetic forceattracting the armature 172. The force of the solenoid 173 tends to openthe valve 167 against the force of spring 166, and thus change theminimum pressure setting of the pressure regulator 60, so as to lowerthe pressure downstream of the metering orifice 61 and increase the flowthrough the datum system 58. This brings into operation the effect ofthe metering restriction 58H to restrict the fuel flow in the datumsystem upstream of the metering restriction 61. The increase in flowthrough the datum system creates a pressure drop between the restrictionSSH and the metering restriction 61, thus lowering the datum pressureacting on each of the nozzle diaphragms of the nozzles 25. When thedatum pressure is lowered, the pressure downstream of the meteringrestrictions 23 is likewise lowered, increasing the pressure drop andthe fuel flow past the metering rods 33 to the nozzles at any particularposition of the rods 33. This priming function is accomplished only whenboth the ignition switch and the starter switch are closed.

Ignition switch fuel cut-0f) circuit In this system, the datum circuitforms a remote control for the discharge from the nozzles. When thepressures between the charging system and datum system are equalized,the fuel discharge from the nozzles is effectively cut off. One mannercontemplated for utilizing this inherent feature is illustrated in Fig.1.

In this particular embodiment, datum line 58 is directly connected withthe fuel chamber A by a pressure equalizing line 300. Communicationthrough the line 300 is in turn controlled by a solenoid operated valveSV, which is spring-biased to an open position and closed byenergization from either of two electric circuits con-' nected withseparate windings in the solenoid valve SV;

The first of these circuits comprises a line 299 connected with theignition switch 197 and extending to one of the solenoid windings of theswitch SV. The lead 298 connects the same winding to the opposite sideof the starter switch S. In this circuit is a vacuum operated switch VS,which is held closed by spring pressure from the spring 250 under normalengine operating conditions.

Operation of ignition switch controlled fuel cut-ofi In the followingdiscussion of the operation of the above-described circuit, the functionof the vacuum operated switch VS will be ignored.

The ignition switch 197 controls the energization of the lead 299, whichin turn, when closed, furnishes the necessary current to one of thewindings in the solenoid valve SV to close the valve against theresistance of the spring 303, which tends to maintain the valve open. Ifthe starter switch is open, as would be the case when the engine isrunning, then this circuit is grounded through the starter motor by wayof the leads 298 and 198. With the ignition switch 197 closed,therefore, solenoid operated valve SV is energized and closed by thecircuit grounding through the starter motor, as described, and thepressure equalizing passage 300 is. inoperative. It will be understoodthat the current flowing through this circuit is necessarily very small,due to the resistance of the solenoid winding, so that it has no efiectupon the operation of the starter motor 195. It requires a much greateramperage to operate the starter motor 195 than it does to operate thesmall solenoid operated valve SV.

When the ignition switch 197 is open, however, the circuit through theleads 299 and 298 is de-energized, allowing spring 303 to open thesolenoid operated valve SV. This equalizes the pressure between the fuelchamber A and the datum line 58, so that each of the valves in the fuelnozzles 25 closes and discharge of fuel immediately ceases.

Conversely, when the ignition switch 197 is turned on, valve SV closes.

Operation of deceleration fuel cut-ofi In the circuit above described isa switch VS operated in response to a negative load on the engine foropening the circuit 299298. Preferably, the switch VS has a diaphragm251 connected through a rod 252 to the switch. The diaphragm 251 issubject to atmospheric pressure on one side, tending to open the switch,and to manifold pressure on its opposite side through the line 108. Aspring 250 may be calibrated so that the switch 253 remains closed untilmanifold suction exceeds the normal range of variations encountered inoperating the engine under its own power. In other words, switch 253remains closed until manifold suction exceeds 21 or 22 inches Hg. Whenthis occurs, the force of spring 250 is overcome, opening the switch 253and de-energizing the circuit 299 and 298 to the solenoid operated valveSV. Spring 303 opens the valve, equalizing the pressure between thechamber A and the datum line 58, so

that fuel discharge from the nozzles 25 is effectively out Unloading If,for any reason, the starting mixture is too rich so that the engine willnot fire during cranking, it is necessary to provide for'some means tounload the engine of fuel. Under these circumstances,'continued deliveryof fuel from the fuel nozzles 25 is not desirable. Here, again, datumpressure regulation forms a convenientmanner for .remotecontrol 'of thedischarge from the fuel nozzles 25.

Whenthe ignition switch 197 and starter switch S are closed, the circuit299 and 298 is short-circuited, so that it becomes inoperative and thecurrent flows directly from the switch S to the starter motor 195through the line 198.

The unloading circuit connects with the line 198, which is energizedunder these conditions, through lines 298 and 304-to the switch TS, andfrom thence through the line 301 through a second winding on thesolenoid valve SV to ground. Thus, normally, 'the valve 8V is maintainedclosed, even though the circuit 298299 is inoperative.

Operation of unloader on the solenoid valve SV is likewise energized,maintaining the pressure equalizing passage closed, so thatthe primingsystem remains'inoperation until the throttle is opened wide. Thismovement of the throttle engages the lug 152 on the throttle arm 52 withthe throttle operated switch TS, which opens the circuit between line304, which is energized, and line 301, which extends to the Winding onthe valve SV. Spring 303 then opens pressure equalizing passage. 300,and the pressurein the charging and datum circuits becomes equalized,closing the nozzle valves 25 to shutoff the discharge of fuel to, theengine.

As above explained, the starter switch S short-circuits the electriccircuit through the lines 298 and 299, so that there is no closing forceexertedagainst the spring 303, and the valve'remains open while thethrottle is held wide open and thestarter switch remains closed.

, The foregoing describes a structure which performs all the functionsand attainsv all the results set forth above, but it is contemplatedthat other. modifications will occur to those skilled in the art whichcome withinthe terms of the appended claims.

I claim:

1. Ina pressurized fuel charging system for a spark ignition type ofinternal combustion engine having a source of electric power and anelectric circuit from the source to the ignition-and to the enginestarter motor including an ignition switch and a starter switch, saidsystem including a fuel'inlet, a fuel nozzle discharging fuel to theengine, a pumpsupplyingfuel' under pressure to'said fuel inlet, a fuelline normally pressurized from said pump connecting said inlet and saidfuel nozzle, a pressure'regulator having amovable wall controlling avalve-in said fuel nozzle, a datum" pressure system, opposed expansiblechambersseparated by said movable wall and connected with said datumsystem and said fuel line, respectively, whereby said regulatormaintains the fuel in said fuel line at a pressure proportional to thecontrolled pressure in said datum system, means for establishing acontrolled pressure in said datum system at a fixed differential withrespect to'said pump supply pressure, a pressure equalizing lineextending between said fuel line andsaiddatumipressure system and anormally open, solenoid closed valve in said pressure equalizingchamber; the combination therewith comprising a pair of windings on saidsolenoid controlled valve, an electric circuit extending from. saidignition switch for energizignition type of internal combustion. enginehaving a source of electric power, an electriccircuit from said sourceto the ignition, an ignition switch, a starterrnotor, a starter motorcircuit, and a starter switch insaid starter motor circuit forenergizing the starter motor from the power source, said systemincluding afuel inlet, a fuel nozzle for discharging fuel-to the engine,a pump supplying fuel under pressure to said inlet, a fuel line normallypressurized from said pump connecting said inlet. and said fuel nozzle,a pressure regulator having amovable wall controlling a Valve in saidnozzle, a datum pressure system, opposed expansible chambers separatedby rsaid movable wall and connected with said datum system and said fuelline, respectively, whereby said regulator maintains the fuel in saidfuel line at a pressure proportional to the control pressure in saiddatum system, means for establishing a controlled pressure in said datumsystem at a fixed differential with respect to said pump supplypressure, a-pressure equalizing passage, and a normally open, solenoidclosed valve in said 'pressureequalizing passageythecombination'therewith comprising apairiof windings in said solenoid for,operating said .valve,.an electric circuit energized byvoperation ofsaid ignition switch .connected with one-of. said windings,.an,,electric circuit energized .by. said :starter switch connected tothe other-of said'iwindin gs, and aconnection forshort-circuiting=said.first circuit onloperationof said starter'switch.

3.;l'n a pressurized fuel charging system for. atspark ignition type ofinternal combustion. engineahaving, a battery and a'starter-i-gnitionsystem including an ignition switch and a starter switch in seriesbetween-the battery and the startermotor, said system including a,fuelinlet, a-fuei nozzlefor discharging fuel totheengine, a pumpsupplying fuelv under pressure to said inlet, a fuelline normally:pressurized from said pump. connecting :said inlet and saidfuel nozzle,a pressure regulatorhaving .a movable wall controlling a valve. in saidnozzle, a datum pressure system, opposed expansible chambers separatedby'rsaidmovable wall andaconnected with :said. datum system and saidfuel .line, respectively, whereby said regulator maintains the fuel insaid fuel line at a pressure proportional to the control. pressure insaicLclatum system, means for establishing acontrolled pressureinsaiddatum system at a fixed diiferential with respect to said pumpsupply pressure, aprcssurecqualizingapassage between said fuel inlet andsaid datum system, and a normally open, solenoid operated valve insaid-pressure equalizing passage;-the combination therewith comprising apair of windingsfor said solenoid operated valve, a first electriccircuit energized from said ignition switch and connectedtoground-through one of said windings and said starter motor wherebysaid circuit is energized only during operation of the enginebut notduring crankin a switch in said first circuit responsive to negativeload on the engine to open'said circuit, and asecond circuit energizedfrom said starter switch and connected to ground through said secondsolenoid winding for retaining-said pressure equalizing passage closedduring operation" of the starter motor.

4. ln aprcssurized fuel charging system'for a; spark ignition type ofinternal combustion engine having a throttle controlled air inlet, abattery and'an ignition switch and starter switch connected in seriesin-anelectric circuit extending from the battery tothe starter motor,said system including a fuel-inlet, a fuel nozzlefordischarging fuelto-the engine, apump supplying-fuel under pressure to said inlet, afuelline normally pressurized from said pump connecting saidinletandsaid'fuel nozzle, a pressure regulator having a movable wall controllinga valve in said nozzle, a datum pressure system, opposed expansiblechambers separated by said movable wall and connected with said datumsystem and said fuel line, respectively, whereby said regulatormaintains the fuel in said fuel line at a pressure proportional to thecontrol pressure in said datum system, means for establishing acontrolled pressure in said datum system at a fixed differential withrespect to said pump supply pressure, a pressure equalizing passagebetween said fuel inlet and said datum system, and a normally open,solenoid operated valve in said pressure equalizing passage; thecombination therewith comprising a pair of windings in said solenoidoperated valve, a first circuit energized from said ignition switch andextending to ground through one of said windings and said starter motorwhereby said circuit is short-circuited during operation of said starterswitch, a second circuit energized by closing of said starter switch andextending to ground through said second winding, and a switch in saidsecond circuit operated by full opening movement of the throttle forde-energizing said second circuit during cranking of the engine.

5. In a pressurized fuel charging system for a spark ignition type ofinternal combustion engine having a throttle controlled air inlet, abattery, an electric circuit extending from the battery to a startermotor, and an ignition switch and starter switch in series in saidcircuit, said system including a fuel inlet, a fuel nozzle fordischanging fuel to the engine, a pump supplying fuel under pressure tosaid inlet, a fuel line normally pressurized from said pump connectingsaid inlet and said fuel nozzle, a pressure regulator having a movablewall controlling a valve in said nozzle, a datum pressure system,exposed expansible chambers separated by said movable wall and connectedwith said datum system and said fuel line, respectively, whereby saidregulator maintains the fuel in said fuel line at a pressureproportional to the control pressure in said datum system, means forestablishing a controlled pressure in said datum system at a fixeddifferential with respect to said pump supply pressure, a pressureequalizing passage between said fuel inlet and said datum system, and anormally open, solenoid operated valve in said pressure equalizingpassage; the combination therewith comprising a pair of windings in saidsolenoid operated valve, a first circuit energized by said ignitionswitch and extending to ground through one of said windings and saidstarter motor, a switch in said circuit opened in response to negativeload on the engine, a second circuit energized by said starter switchand extending to ground through said second winding, and a switch insaid second circuit operated upon movement of said throttle to thewide-open position for de-energizing said ,second circuit.

References Cited in the file of this patent UNITED STATES PATENTS2,785,669 Armstrong Mar. 19, 1957

